System of electrical distribution.



No. 728,259. PATENTEDMAY 19. 1903.

A. 1). LUNT.

SYSTEM OF ELECTRICAL DISTRIBUTION.

APPLIUATION FILED NOV. 30. 1900 no MODEL.

Fig.1. I W

Witnesses UNITED STATES Patented May 19, 1903.

PATENT OFFICE.

ALEXANDER D. LUNT, OF SOHENEOTADY, NEW YORK, ASSIGN OR TO GEN- ERALELEOTRIOOOMPANY, A CORPORATION OF NEWV YORK.

SYSTEM OF ELECTRICAL DISTRIBUTION.

SPECIFICATION forming part of Letters Patent N 0. 728,259, dated May 19,1903.

Application filed November 30, 1900. Serial No. 38,087. (No model.) I

To all whom it may concern..-

Be it known that I, ALEXANDER D. LUNT, a citizen of the United States,residing at Schenectady, county of Schenectady, State of New York, haveinvented certain new and useful Improvements in Systems of ElectricalDistribution, of which the following is a specification.

My present invention relates to certain imre provements of particularvalue in connection with that type of dynamo-electric machine which isadapted to receive current from or deliver current to either analternating-current system or a direct-current system, an example ofwhich type of machine is represented by the well-known rotary converter.

My invention when applied to such a machine largely reduces the heatingof the armatureconductors and at the same time improves the commutationof the machine, therebyincreasing the output and improving theefficiency of the machine. As the best means for explaining my inventionI have hereinafter described the same as applied to a twelve-,

phase rotary converter for changing alternating current into directcurrent, or the reverse,

as may be desired; but it is to be understood that it is not to belimited to use in this connection alone.

As to the points of novelty which characterize my invention, the claimsappended hereto are intended to clearly point out the same.

In the drawings, Figure 1 is a diagrammatic representation of myinvention, and Fig. 2 an explanatory diagram of electromotive forces.

Fig. 1 represents, among other features, a system of connections wherebythree-phase current may be converted into twelve-phase current andsupplied to the armature of a 0 dynamo-electric machine, the conversionbeing effected through the instrumentality of a system of transformersthe windingsof which are interconnected, so as to form three distinctpolygons of electromotive forces, two

of the polygons representing a triangular re-' lation of electromotiveforces and the third a connection of electromotive forces in such a waythat they may be represented by a hexagon. These various relations ofelectromo- 5o tive forces will be made clearer by reference to Fig. 2,which upon inspection will be seen to disclose a triangle the ends ofthe sides of which are nu mbered'from 1 to 6,successively, areversely-arranged triangle, (numbered from 1 to 6', inclusive,) theremaining figure being a hexagon the sides of which are indicated by thenumerals in this figure not already referred to. The various angles ofthese polygons will be seen 4 to intersect the circumscribing circle attwelve points equally spaced from each other. These points ofintersection are represented in Fig. 1 by the taps connected tocorrespondingly-designated points in the armature-winding 1 of therotary converter therein shown. These taps are con- .nected to a seriesof collector-rings 2 to 13,

inclusive, by means of which current is conveyed either to or from thearmature-winding 1, .the collector-rings in turn being connected to asystem of transformers in which the electromotive forces have therelations represented in the diagramin Fig. 2. To

. make clear these connections, the various taps about'thearmature-winding 1 are designated by pairs of numerals identical withthe numerals applied to designate the ends of the transformer windingsto which these taps lead. The transformer-windings to which referencehas thus been made consist of three sets of secondary windings, each setcomprising four secondaries inductively related to a single primary.These primary windings are indicated at 14,15, and 16 and are connectedin any suitable manner to a three-phase supply-circuit. The sets ofsecondaries corresponding to these primaries are connected together, sothat their electromotive forces are interrelated,in a manner representedby the diagram in Fig. 2, it being understood, of course, that theseveral secondaries are so proportioned as to give elec- 9c tromotiveforces of the relative values represented by the lengths of the sides ofthe various polygons in Fig. 2. Upon this understanding the connectionswill nowibe pointed out. I

As a basis for making the connections shown three secondaries areselected0ne from each set-and are connected in delta relation in anordinary manner, the selection being made arbitrarily from the varioussecondaries constituting each set. The secondaries selected in thisparticular case are numbered 1, 2, 3, 4:, 5, and 6, the connectionsbeing made so that the closed circuit constituting the delta connectionincludes the windings in the order in which the numerals are given. Thisconnection of secondaries is represented by thecorrespondiugly-designated triangle in Fig. 2. The next step is toconnect up three more secondaries, so as to produce a relation ofelectromotive forces represented by the second triangles l to 6,inclusive, which forms with the first what may be termed a double delta.The parallel sides of these reversely-arranged deltas are designated bythe same numerals, but are distinguished from each other by a suitableexponentas, for example, the exponent The sides of the two trianglesbeing thus numbered, so that corresponding ends of parallel sides arerepresented by the samenumerals suitablydistinguished from each other,no difficulty will now be found in connecting up a set oftransformer-secondaries to represent the second triangle, theconnections in this case being of course made so that the circuit passesthrough the windings in the order in which the nu merals are placed onthe second triangle in Fig.2 that is to say, in the order 1 2 5 6 3 4titbeing understood, of course, that corresponding terminals of each of thesecondaries constituting a set are represented by the same numeral as abasis, these numerals, however, being distinguished from each other, asabove mentioned, by means of suitable exponents or otherwise. Theconnections for the triangle last mentioned may thus be readily tracedin Fig. 1 without further explanation. The connections between theremaining transformer-secondariesare such as to include them insix-phase relation to each other, as represented by the hexagondescribed within the circle in Fig. 2. As a conveniencein making theseconnections the diagram in Fig. 2 may serve as a guide. In this diagramthe sides of the hexagon are numbered, so that the ends of each side aredesignated-by characters having the same basic numeral as is ap plied tothe corresponding ends of the sides of the triangles parallel thereto.Thus, for example, the triangle 1 to 63, inclusive, has the side 1 2parallel to the side 1 2 of the hexagon. The side 3 4 of this trianglecorresponds in phase to the side 3" 4: for the hexagon, and so on.Inasmuch as the parallel sides of the various polygons in Fig. 2correspond to secondaries of the same phase,no difficulty will now behad in making the proper connections to obtain the hexagonal relation ofelectromotive forces in Fig. 2, these connections being made such thatthe closed circuit resulting includes the secondaries in the order ofthe numerals applied to designate the same. Thus, for example, thecircuit may be considered as starting at the terminal then through thissecondary to the other terminal 2", then through secondray 6 5, thenthrough the secondary 3" 4;", and so on.

From points in the connections which interlink the various secondariesin the manner described leads extend to and make contact with thecorresponding collector-rings 2 to 13, inclusive, as will readily beunderstood. The collector-ring 2, for example, leads from the pointdesignated 4 6 in the armaturewinding to the connection which joinstogether the similarly-designated ends of the transformer secondarieswhich cooperated with the winding. In the arrangement thus described itis to be observed that the currents which circulate in thetransformerwindings are in phase with the electromotive forces inducedtherein, and are therefore of minimum value,which condition would not bethe case if the currents were out of phase with the electromotive forcesof the windings. This arrangement therefore permits the employment of aminimum amount of copper, securing decreased cost and increasedefficiency. Another valuable advantage is the cross connection betweenthe various points of the armature-winding afforded by the varioussecondaries connected thereto. This cross connection serves to balancethe electromotive forces acting about the armature-winding, therebypreventing large and useless cross-currents in the armature-winding, andso securing better commutation, which is an important matter in machinesof this character.

It is of course to be understood that the rotary converter,thearmature-winding of which is indicated at 1, is to be provided with theusual commutator 17 and with a properlyarranged field-magnet structure,which for the present purpose it'has not been found necessary toillustrate. The direct-current mains 18 19 are connected to brusheswhich bear upon the commutator 17 in the ordinary manner.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is-

1. The combination of aplurality of transformer windings inductivelyrelated to a three-phase circuit, connections such as to interlink someof the windings in doubledelta relation to each other, and connectionsbetween other windings interlinking them in closed circuit so that theelectromotive forces between their terminals bear a six-phase relationto each other.

2. A dynamo-electric machine, a set of machine, three sets oftransformer-windings, the windings of each set being connected in closedcircuit,and leads extending from points in the connections whichinterlin'k the windin gs of each set to points symmetrically located inawinding of said dynamo-electric machine.

4. A dynamoelectric machine, six transformer-windings connected inseries with each other, and connections between the terminals of the sixwindings and said dynamo-electric machine.

5. The combination of three sets of transformer-windings, each setconsisting of windings arranged in closed circuit, and operativeconnect-ions between a dynamo-electric machine and said sets oftransformer-windings.

6. A twelve-phase dynamo electric machine, and leads extending from saidmachine and connected to three sets of sources of electromotive force,each set including a plurality of sources.

7. A dynamo-electric machine, a set of transformer-windings connectedtogether so that the terminal electromotive forces have a six-phaserelation to each other, other transformerwindings connected indouble-delta relation to each other, and connections between saidtransformerwindings and said dynamo-electric machine.

8. The combination of sources of electromotive force connected indouble-delta relation to each other, other sources of electromotiveforce connected in series so as to produce resultant six-phaseelectromotive forces, and a dynamo-electric machine operativelyconnected to said sources.

9. The combination of three distinct sets of windings, connectionsinterlinking each of said sets in a closed circuit, a dynamo-electricmachine, and connections from terminals of said windings to pointssymmetrically located in the armature-winding of said dynamo-electricmachine.

10. The combination of a plurality of windings some of one electromotiveforce and some of a difierent electromotive force, connectionsinterlinking windings of like electromotive force in closed circuit,other connections interlinking windings of electrometive forcesdiffering in magnitude from the electromotive forces of the first set ofwindings, and a dynamo-electric machine having its armature connected toterminals of said windings.

11. The combination of a plurality of windings, connections interlinkinga given number of the windings in closed circuit, other connectionsinterlinking a difierent number of said. windings in closed circuit, adynamo-electric machine, and electrical connections fromsymmetrically-located points in a winding of said dynamo-electricmachine to terminals of said windings.

12. The combination of a dynamo-electric machine having an armatureprovided with a commutator and collector-rings, a plurality oftransformer windings, connections between said windings interlinkingthem in a single closed circuit so that the electromotive forces betweenthe terminals of the windings as thus connected bear a six-phaserelation to each other, and connections between said terminals and saidcollector-rings.

13. The combination of a dynamo-electric machine,a plurality oftransformer-windings, connections between some of the windingsinterlinking them in a closed circuit so that the electromotive forcesbetween their terminals bear a six-phase relation to each other, andconnections or leads extending from all of said windings to pointssymmetrically located in a winding of said dynamo-electric machine.

14. The combination of six windings connected in series with each other,means for developing in said windings alternating electromotive forcesrelated to each other in phase like the sides of a hexagon, and adynamo-electric machine having alternating current-leads connected tothe junctions between said windings.

15. The combination of a dynamo-electric machine having leads extendingfrom awinding thereof in sixphase relation to each other, sixtransformer-windings connected in series with each other, andconnections between said leads and the six junctions between saidtransformer-windings.

In witness whereof I have hereunto set my hand this 28th day ofNovember, 1900.

ALEXANDER D. LUNT.

Witnesses:

BENJAMIN B. HULL, MARGARET E. WOOLLEY.

